Banner EZ-SCREEN­ Safety Light Curtain Systems - Manual (Page 15)

Formula and Examples
The Safety (separation) distance formula for U.S. applications:
Ds = K x (Ts + Tr) + Dpf
The minimum distance formula for European applications:
S = (K x T) + C
where:
U.S. Applications
Ds
the safety distance, in mm (inches).
K
1600 mm per second (or 63" per second), the
OSHA 29CFR1910.217, ANSI B11.19, ANSI/RIA
R15.06 recommended hand-speed constant
(See Note 1 below)
Ts
the overall stop time of the machine (in seconds)
from the initial “stop” signal to the final ceasing of
all motion, including stop times of all relevant
control elements (e.g., IM-T-.. Interface Modules)
and measured at maximum machine velocity
(See Note 3 below).
Tr
the maximum response time, in seconds, of the
EZ-SCREEN Type 2 emitter/receiver pair (de-
pending on model).
Dpf
the added distance – in this case, 78 mm (3") –
due to depth penetration factor as prescribed in
OSHA 29CFR1910.217, ANSI B11.19, ANSI/RIA
R15.06 for U.S. applications .
European Applications
S
the minimum distance, in mm, from danger zone
to light screen center line; minimum allowable
distance is 100 mm ( 175 mm for non-industrial
applications), regardless of calculated value.
K
hand-speed constant (see Note 2); 2000 mm/s
(for minimum safety distances < 500 mm) 1600
mm/s (for minimum safety distances > 500 mm)
T
the overall machine stopping response time (in
seconds), from the physical initiation of the safety
device and the machine coming to a stop (or the
hazard removed). This can be broken down into
two parts: Ts and Tr where T = Ts + Tr
C
the additional distance, in mm, based on intru-
sion of hand or object towards danger zone prior
to actuation of a safety device.
Calculate using the formula:
C = 8 x (d - 14)
where d is the resolution of the light curtain (for d
< 40 mm). For EZ-SCREEN Type 2, d = 30 mm
and C = 128 mm (5").
Notes:
1. The OSHA-recommended hand speed constant K has been determined by various studies and, although these
studies indicate speeds of 1600 mm/sec. (63"/sec.) to more than 2500 mm/sec. (100"/sec.), they are not conclu-
sive determinations. Consider all factors, including the physical ability of the operator, when determining the value
of K to be used.
2. The recommended hand speed constant K, derived from data on approach speeds of the body or parts of the
body as stated in ISO 13855.
3. Ts is usually measured by a stop-time measuring device. If the machine manufacturer's specified stop time is
used, at least 20% should be added to allow for possible clutch/ brake system deterioration. This measurement
must take into account the slower of the two MPCE channels, and the response time of all devices or controls
that react to stop the machine. See Notice Regarding MPCEs. If all devices are not included, the calculated sepa-
ration distance (Ds) will be too short and serious injury could result.
EZ-SCREEN® Type 2 Light Screen Instruction Manual
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